I recently got into a debate about the efficacy of bicycle helmets and — as someone who wears a helmet religiously and credits one with once saving me from serious injury — I was amazed to find that the research into this subject is… well, I’m not sure if “messy” or “inconclusive” is the right word:

As with many things, the question is more complex than it may at first appear. It might seem at first that the question is straight-forward – do bicycle helmets work? But what exactly is meant by this? Most people might assume that this means – if you are riding a bicycle and get into an accident, will the helmet reduce the severity of the resulting head injury?

We could, however, ask several other reasonable questions related to using a bicycle helmet:

Is a rider more likely to get into an accident if they are wearing a helmet? Does wearing a helmet affect the riskiness of the cyclists behavior, or does it affect the behavior of vehicle divers that might threaten cyclicsts?

What are the net effects of bicycle helmet laws? Do they discourage bike riding, and if so what is the net health effect of decreased riding?

Are there other more effective methods of protecting the safety of bicycle riders?

The first question is perhaps the easiest to answer, and the answer is a resounding, yes! Helmets do work in that they reduce the severity of head injury if you are involved in an accident. This is the common sense result as well. If your head is going to smash into something hard, you want a protective cushion between your skull and the hard object.

No randomized controlled trials were found. This review identified five well conducted case control studies which met our selection criteria. Helmets provide a 63%-88% reduction in the risk of head, brain and severe brain injury for all ages of bicyclists. Helmets provide equal levels of protection for crashes involving motor vehicles (69%) and crashes from all other causes (68%). Injuries to the upper and mid facial areas are reduced 65%.

The best data we have shows that helmets are pretty effective. The lack of controlled trials means that no one has done a study where cyclists were randomized to either wearing a helmet or not wearing one, but that seems like a minor problem for the question at hand – if you are in an accident, helmets reduce the risk of serious head or facial injury.

It could, however, mean that cyclists who choose to wear helmets also engage more generally in safer behavior, leading to fewer or less serious accidents. This does seem to be the case. Some feared that cyclists who wore helmets would engage in riskier behavior because of a sense of security, but the opposite is true – helmet wearers are safer. Some of the observational data, however, looks at those who are in an accident, not the risk of being in an accident, so this does not take away much from the data showing that helmets are effective.

This brings us to bicycle helmet laws, which remain controversial despite the fact that helmets themselves seem to work. A 2006 review concluded that in locations where bicycle helmet laws are enacted compliance with helmet use does go up, especially among adults, but has little effect on trends in head inuries.

Other researchers disagree, however. In a 1998 study helmet use increased significantly, 13 fold, after a helmet law was passed, and this also decreased the incidence of head injuries.

Bicycle helmet legislation appears to be effective in increasing helmet use and decreasing head injury rates in the populations for which it is implemented. However, there are very few high quality evaluative studies that measure these outcomes, and none that reported data on an possible declines in bicycle use.

Regarding decline in bicycle use, this remains controversial as well. The Australia study cited above showed a decline in bicycle use after helmet laws were passed. A study in Canada, however, showed no decline in ridership. Perhaps climate is a factor. Also, the Australian study was challenged for not showing the duration of the decline in riding – perhaps it is very transient.

This is an important issue because bike riding is associated with a decreased risk of cardiovascular disease. A shift from riding bikes to driving cars may have a greater negative effect on health than the benefit from wearing helmets. But this remains an open question needing further research.

There are also other measures, other than helmets, that can improve the safety of riders. In countries that have many bicycle riders, like Holland, riding safety is much greater. This is likely for two reasons. When there are more riders, car drivers are forced to be more aware and careful about those riders.

Also, Holland has a significant bicycle infrastructure - special paths just for bikes that separate them from vehicle traffic.

Conclusion

Bicycle helmets work. The overall evidence suggests that if you ride a bicycle, especially on the streets, you should wear one.

Bicycle helmet laws increase compliance with wearing helmets, but it is currently unclear if they reduce head injuries and if they reduce overall bicycle use. Further study is needed to answer these questions.

Having bicycle paths that separate bikes from cars is effective in reducing accidents with no apparent health downside. If you drive in a city or town where there are bicyclists, then be especially careful and give them a wide berth, even if they are wearing a helmet.

32 Responses to “Bicycle Helmets”

A study from the National Bureau of Economic Research (http://www.nber.org/info.html) suggests helmet laws for children reduces ridership, and perhaps encourages involvement in other activities for which helmets are not mandated by law.

Here is my hang-up. First I wanted to say that fatal bicycle accidents really shouldn’t be blamed on the cyclist. Perhaps it is true that they “cause” some accidents, but my thinking is that the person in the huge metal vehicle should have a greater duty of care when it comes to avoiding accidents (and I think they do, in law). Bicycles crashing into each other, and, God forbid, pedestrians, is bad, but it’s no epidemic plague like we see with motor vehicle accidents. So I’m already ready to get righteously angry with motor vehicle operators (although the majority are safe and responsible).

Next though, we’ve seen all these arguments in favour of cyclists wearing helmets. But the main factor isn’t the fact you’re on a bicycle; it’s the fact you’re in traffic at all. Pedestrians (and segway riders, and roller bladers, and skateboarders) face exactly the same risk as cyclists when they’re in the road. If there are going to be laws for cyclists to wear helmets, shouldn’t there also be a law for any pedestrian who interacts with traffic? Wouldn’t helmets for pedestrians also reduce injury and reduce mortality?

Has there been a study in Holland since motorized scooters were allowed on the bike paths? When we visited Amsterdam it seemed that the greatest danger were to the pedestrians waiting to cross the street, especially from mopeds.

Also, unlike the city I live in: most of the Netherlands is fairly flat, not just North and South Holland. Even Maastricht, an awesome place to visit, is flatter than where I live (some streets literally turn into staircases, there is also a four story elevator ride from the front of the main library to the back entrance). It is so much fun to see a bike barreling down the hill past my house (especially since some ignore stop signs), and even more fun to see them roar down a steep viaduct that crosses a ravine.

I guess the one thing missing from this analysis is a comparison between relative risk – the 63%-88% who benefit when in an accident – versus absolute risk – what is the probability of me needing a helmet if I go out for a “typical” ride. I realise the latter is highly affected by a number of factors: amount of traffic, riding skill, road quality, etc., but I’m curious as to the quantifiable risk I take when not wearing a helmet and biking around suburban streets at a reasonable pace.

The last time I looked at the data I could find, it seemed to me that it was much more in my best interest if I wore a helmet in my car, rather than on my bike. But nobody (yet) seems to be proposing helmet laws for automobiles. (… or perhaps for in the shower, now that I think about it.)

@ Steve Novella
“If you drive in a city or town where there are bicyclists, then be especially careful and give them a wide berth, even if they are wearing a helmet.”

I am a avid cyclist. That comment spurred an interesting thought. Are you saying that the evidence shows a effect resulting in auto drivers being less cautious around cyclists if they are wearing a helmet?

There are minimal dedicated cycling paths in the US northeast, certainly not for regular commuting. Most of my riding is on active roads. So you see how that finding would be concerning to me.

“Wouldn’t helmets for pedestrians also reduce injury and reduce mortality?”

What is the head injury rate among pedestrians per hour of walking?

What is the head injury rate for cyclists per hour of cycling?

What is the head injury rate for passengers in an automobile per hour of driving? (which may actually be significant enough that our most recently purchased vehicle has side air bags to protect the head, and of course, there are seat belts to keep your head from hitting the dashboard/front window)

Maybe that’s one of those mean things we aren’t supposed to do any more. Allow me to rephrase.

If the biker is at fault in either the legal or common meanings, that typically implies the the driver was already being careful and the biker was not. So it doesn’t help any to suggest that one party or the other should be careful, regardless of the damage potential.

Vehicles are indeed dangerous, but that’s why we have all of these rules for both bikes and cars. Bikes aren’t supposed to swerve in front of cars–not because the driver is necessarily apathetic, but because it is not within the vehicle’s physical ability (or the driver’s mental ability) to avoid everything.

@ChrisH, thanks for looking out! I have had too many close calls with people opening car doors right in front of me. Though its hard to fault drivers for this because it is easy to miss seeing a bike even if you do a good mirror check. We’re small and fast. That’s why I always wear a helmet and bright gear, its too hard for drivers to see us and as a biker you eventually get hit.

Though I have had cyclists look warily at me as I wait to open my car door. Some are expecting me to open it just in time to cause them to impact the door. But, a cautious cyclist is a safer cyclist. I don’t blame them. There have been news reports of drivers deliberately hitting cyclists, and recently one who drove over the curb to hit people waiting at a bus stop.

I also yell and honk at people who run red lights. I just had that happen when someone ran the red light for a hard left turn on a five-way intersection (known locally as “five corners”). The problem was that while running that red light he almost hit me as he cut me off as I went through the slight left turn (almost straight). He actually saw where I turned, and wen down that street to ask me why I honked at him. I told he ran a red light. He did a mock “Oh, I did not know that.” To which I can only respond: Look at the light.

At that particular light it used to be common for those in the far left lane to cut off those going up the near left lane street. It was dangerous and caused many accidents (along with those who turned left without looking for on coming traffic coming down the hill). So the city turned the blinking yellow to a red light, so if someone decided to change lanes in the middle of the intersection it would be when most of the traffic had gone up to the street indicated by the near left light and less likely to cause a collision.

By the way, I am always wary at that intersection. When I am in the near left turn lane, I always look at the driver in the far left turn lane. Before he ran the red light, he was looking at his cell phone and not the traffic light. Usually a short beep of my horn makes them look up at the actual traffic light, and they stop. This guy thought the beep was a signal to power forward and almost tear off my front bumper.

Though it was quite fun that he actually took the initiative to ask me what my “problem” was. So I told him: I hate people who run red lights. I did not actually tell him to not look at his phone, which is probably what is the real reason he did not know he had a red light.

For some odd reason there are stop light cameras on the main road (it is a state highway), but not on the cross lanes, or any of the left turn lanes. That is annoying. The city could get lots of revenue off of those who cannot read simple symbolic signs. Like arrows, and… wait for it… traffic signals.

The issue of helmet usage on bicycles always perplexed me, not being a cyclist, but having been an alpine skier all my life I understand the need for helmets in any sport where the risk of head injury is increased by high speeds, height from the ground and unforgiving obstacles. Years ago the only people who utilized helmets, as I did, while ski racing. This began to change after a few high profile deaths (Sonny Bono and I believe one of the Kennedys) that purportedly could have been avoided with the use of helmets. The media attention raised awareness of helmet usage however was slow to catch on. It was not until manufacturers of the helmets began to design their products with style in mind as much as safety that the use of helmets in skiing and snowboarding became ubiquitous. Now it is rare to see anyone skiing, here in Colorado at least, without a helmet and as far as I know there are no laws or policies at any resorts that mandate the use of them.
If any group is interested in raising the level of helmet usage on bicycles the industry will have to design helmets that are comfortable and fashionable for the average user. The headgear available today just makes you look like a Mormon doing missionary work.

The wearing of bicycle helmets is compulsory in Australia and, really, nobody gives it a second thought. All the riders in the Tour de France wear them, providing excellent role models. And they’re fashionable. Seat belts are also compulsory in Australia and, likewise, nobody gives them second thought. And, likewise, racing car drivers all wear them providing excellent role models. After a while, it doesn’t feel safe not to wear car seat belts or bicycle helmets.

I took up road cycling for three months last year because tendonitis prevented me from running. I had one near hit when a motorist threw open his door and stepped out to cross the road. I nearly collected both him and his door. It gave him more of a fright than it did me because I was ready and able to take evasive action if needed. There were also several incidents of drivers offering abuse or trying to scare me off by driving really close while overtaking and then swerving into my path of travel. This didn’t work. As a result of my experiences I am always mindful of, and courteous to, cyclists especially those I pass in my car on the way to my Sunday morning runs in the hills now that my tendonitis has healed.

Maybe it should be compulsory to be a cyclist for three months before you can get your car licence. |:

“Use” vs. “Utilize” – Fair point, however I find it quite funny that those who make this point (Google misuse of utilize) refer to the dictionary definition “to make use of; turn to practical use or account.” (Miriam Webster) to say that utilize indicates the use of something above or outside its intended use, implying that it is not exactly synonymous with “use”. Why I find that funny is that the very same dictionary list “Use” as a synonym for “Utilize” and in that same dictionary “Underutilize” is defined as “to utilize less than fully or below the potential use”. Therefore, in the instance in my last post, utilize is used as an antonym for “Underutilize”. You see in the context of the post, helmets are a readily available commodity that is UNDERUTILIZED by the population, so the opposite condition would logically be UTILIZED. I believe this is solid enough ground for my use of the word.

@Thadius You “the need for helmets in any sport where the risk of head injury is increased (…)”, but cycling is not just a sport, it’s a mode of transport just like walking or driving!

I don’t really understand this helmet-debate. Why focus on reducing the risk of major injury *when in an accident* instead of reducing the risk of accidents? The dutch cycle en masse and don’t wear helmets, but somehow they’re not all dying from head trauma; they must be doing something right. A few months ago I came across a very nice blog called Bicycledutch which highlights dutch cycling and infrastructure, I recommend it to anyone who’s interested in cycling: https://bicycledutch.wordpress.com/ or twitter @bicycledutch

The idea that drivers would be more careless around helmeted cyclists is disturbing in it’s implications.I hope that this is not well founded,but I will continue to wear my helmet anyway,because there are many other ways to crash on a bike besides being hit by a car.Wet and irregular pavement,loose gravel,animals darting in front of you,and other cyclists come to mind as potential hazards.
Just as an aside,I see many bikes that are not equipped with a rear view mirror,and that is an important piece of safety equipment as well. Knowing what’s coming from behind gives you more of a chance to protect yourself.

Just as an aside,I see many bikes that are not equipped with a rear view mirror,and that is an important piece of safety equipment as well. Knowing what’s coming from behind gives you more of a chance to protect yourself.

That is something I definitely want to get for myself. There is a very popular bike trail near where I live (it was train tracks until the 1970s), and I need to be able to check to see if there are faster cyclists coming from behind before I pass pedestrians.

I often walk on that trail to get to a shopping center. Last winter I was walking to pick up something at a store at four in the afternoon, and it was already getting dark. A cyclist came up behind and commented he could not see me in the dim light. I thanked him, and the next time had a flashlight. On my birthday I got a reflective hat, which I now always where on walks.

The trail also goes through the outer sections of a state university. On those sections it gets very crowded, especially around sports events and in a couple of years there will be a light rail station (right in between the football stadium and medical center). So the university has plans to widen the trail, where possible (part cuts into the side of a very steep hill) there will be separate parts for cyclists and pedestrians.

Thadius,
Well, let’s just say, you found a justification for your mistake

tmac,
During my three months of cycling I often wondered about rear vision mirrors. I virtually never see them in use here. But you can’t really get a good view looking backwards over, around, or under your shoulder and it keeps your eyes off the road ahead for too long, especially if riding at speed.

Chris,
I also have a bike trail near where I live and, likewise, it is a converted railway line. It extends 40km from Lillydale to Warburton and is pretty flat. I used to ride my hybrid bike along that trail to Warburton and back before discovering hill running.

BillyJoe7- A well designed mirror that is of adequate size and just the right amount of convex,can give you good,easy to check view from behind. I have ridden with and without a mirror,and the peace of mind that comes from having that extra piece of information about your surroundings,is well worth it.
Just as you commented about seat belts and helmets,once you are accustom to having that safety feature,you feel vulnerable without it.

Thanks for the interesting article.
Perhaps I should paint my helmet to resemble a head so that car drivers take a bit more care.
The risk homeostatsis argument is often UTILIZED by the anti-helmet law brigade.

As a cyclist and motorcyclist, who always wears a helmet, this whole subject still makes my teeth grind, for several reasons:

1. The vast majority of accidents are caused by the uncontrolled, unskilled, or inattentive acts of people driving incredibly dangerous objects.

Mandating helmets for cyclists is the equivalent of mandating children wearing body armour as a response to school shootings. Driving should only be undertaken by highly skilled, professionals, as is the case for busses, trucks and heavy equipment. No logical distinction exists, to my mind, between a sedan, and a Cessna.

2. Helmets would make EVERYTHING “safer”, including travelling in cars. Yet, while car drivers constantly harp on about how others should wear uncomfortable, expensive, restrictive objects on their heads and bodies (to keep them somewhat less vulnerable to the dangers mostly posed by car drivers), car drivers would never themselves agrree that car occupants should wear helmets and fire-proof clothing.

I have a simple, cheap, suggestion that would reduce the road toll to near-zero overnight: Remove the driver’s seat belt and air bag from every car, and install a two-foot shiny steel spike protruding from the centre of the steering wheel, pointing directly toward the driver’s chest.

Vehicle drivers, however, appear to give bicycle riders without helmets more room than those with helmets. So wearing a helmet may make it more likely to be hit by a car while riding a bike.

I wondered about this and realized two things. Firstly, most accidents don’t happen because a car has rammed a bike off the road sideways. They happen at junctions or because the bike wasn’t seen at all. Secondly if I see someone without a helmet, I instantly assume they are not going to be a regular rider so are going to be careless, unpredictable and wobbly. I would give extra berth to a learner driver for the same reason.

What’s funny is that the people who wouldn’t dream of protecting themselves with a helmet are the same people that, when getting into a car seem to forget they have a seat-belt, air bags, basic roll cage, special designs that crumple the car to absorb the energy, adjustable wrapping head rests to protect against neck injury, ABS brakes and probably a few other things. Not to mention the number one reason I always hear for the SUV, that it’s big so it’s protective.

But no, we definitely shouldn’t put on a small, light helmet and maybe wear some bright clothes when hurtling along a road on top of a bit of metal and some rubber.

What’s funny is that the people who wouldn’t dream of protecting themselves with a helmet are the same people that, when getting into a car seem to forget they have a seat-belt,…

Many many years ago, a group of us from work piled into a car to go to lunch. One person in the back commented: “Well, I guess we are required to put our seat belts on now!”. To which I replied that the lap belt I had worn as a teenager was why I still had a face. I was in the front seat of an old 1960s car, and we had a fairly slow speed head on collision. I have a vivid memory of the dash board getting closer to my head, and then I bounced back. Because it was just a lap belt, I ended up with a couple of broken ribs and a weekend in the hospital (the doctor wanted to make sure I had bruised my spleen). Even though those ribs hurt for a couple of years, it was better than having my head hit the dashboard (or go through the window).

Needless to say, the person who made the quip about seat belts did not open her mouth again about vehicular safety devices.

(oh, and talk about faulty memory: I always remember the oncoming car as being red, I was told later it was actually blue)

I can’t count how many times my helmet saved my bacon mtn biking. I wouldn’t even go mtn biking without a helmet, I guess that’s a case where ricky behavior is increased with helmet usage, but truthfully, I want to engage in risk but I also want to keep my head intact. I also dirtbike and would never even consider riding without a helmet.

But lately, the argument I get in is with old friends about ski helmets. Now we all grew up in Park City, UT a ski town, and I think some of us now in the 40′s are just denying them because they think they are silly and yet come up with these rationalizations as an excuse. As someone who got knocked out twice skiing, it was a no brainer (ha!) for me. The moment came when I caught an edge at the top of a chute, and went down head first. It’s a very steep run, trees everywhere, and I remember saying to myself, If I make it through this, I’m getting a helmet. And I did. It has come in handy skiing tress when I didn’t duck low enough and hit a branch. You could say the helmet made me more careless but honestly, ahem, I have done that before. Hey sometimes you think you’re clear, and then crack! Also, one time the safety bar (ha!) hit me in the head on the lift.

As for Holland, a place I have visited many times, things are different there. They have much more of a bicycling culture and that is reflected in how they ride and respect each other. I was told that bicycles have the right of way over cars and pedestrians.

But the final thing for helmets for me is, sometimes you can have just the smallest accident, no other bike or car or person involved, just one of those ‘doh!’ moments, and you clunk your head on the curb and it’s all over. Head trauma sucks, you got one brain, protect it.

I do agree on how unstylish bike helmets still are, but until I find that perfect cool helmet, I guess I’m stuck with my dorky Giro. Hey, at least it’s got a sun visor!

Many years ago I did a study on bicycle related injury in rural town and had great interest in promoting the use of cycling helmets. I still see lots of injuries, but far fewer kidney donors.
When considering children it is important to consider the mass of the helmet, and the risk of penetration. Hard shell helmets reduced penetration risk, but have a greater mass and increase the risk of cervical injury, soft compressible and light helmets appear to be the best compromise.
Full face motor cycle helmets avoid this by transferring the force onto the clavicles, thus someone who head plants from a motor will present with fractured clavicles instead of being quadriplegic.
It was suggested that car drivers should be compelled to wear helmets – there has been an increase in head injuries for drivers T-boned by large 4WD (SUV), where the front of the larger vehicle is at the perfect height to penetrate the victim vehicle at the level of the driver’s head.
Why do we legislate to protect people from uncommon events and ignore them being conned by the altmed industry which results in far more preventable deaths? Chiropractors kill more people by inducing strokes that die from cycling head trauma.